Lumbar spondylolisthesis is a condition involving misalignment of the vertebrae in the lumbar portion of the spinal column, which condition is either developmental, acquired, or traumatic in origin. This condition typically occurs because of a discontinuity between the superior and inferior articular facets of a vertebral segment in the area known as the pars interarticularis. The resulting deformity occurs because of forward displacement of the superior vertebrae with respect to the inferior vertebrae located immediately therebelow, these vertebrae being connected by an intervertebral disc. Spondylolisthesis is classified by grade with Grade IV being the most severe. In a Grade IV situation, the superior vertebral body is completely displaced forward over the inferior vertebral body. Since the spinal canal and its contents lie immediately posterior to the vertebral body, instability with or without displacement of the vertebral body can result in compression or traction forces affecting the adjacent neural elements. These forces may produce either back or leg symptoms or both.
Spondylolisthesis is more common is young athletes, particularly, gymnasts and cricketers, where the spondylolisthesis is thought to result from stress fractures of the pars interarticularis due to recurrent stresses during extension of the spine. In elderly patients spondylolisthesis can occur without a spondylolysis due to degenerative changes in the facet joints of the spine and lax ligaments, a condition typically called degenerative spondylolisthesis. Although spondylolisthesis usually presents itself as low back pain, if the forward vertebral slip or displacement is sufficiently severe, the exit foramen for the nerve roots at the level of the spondylolisthesis may become narrowed thereby leading to nerve root entrapment and radicular symptoms.
Treatment of conditions involving misalignment of the vertebrae continues to be a challenge and a wide variety of different tools, implants, and surgical techniques and/or methods for correcting a spinal deformity have been develop to address not only spondylolisthesis reduction, but other spinal and vertebral deformities including intervertebral disc herniation. See, for example, the various surgical tools and methods of use disclosed in U.S. Pat. Nos. 5,536,268; 5,599,279; 5,601,556; 5,653,761; 5,658,336; 5,697,889; 5,697,977; 5,797,910 and 5,800,550. Although the above-identified prior art discloses a wide variety of different means for either inserting a disc implant or for spreading apart adjacent vertebrae, only U.S. Pat. Nos. 5,697,977 and 5,601,556 disclose any type of tool for accomplishing a spondylolisthesis reduction. In this regard, importantly, the present surgical tool and method of use differs both structurally and operationally from all of the prior art devices including the surgical tool disclosed in U.S. Pat. Nos. 5,601,556 and 5,697,977 relating specifically to spondylolisthesis reduction. Also, importantly, none of the prior art devices permit reduction of vertebral displacement via an anterior or intra-abdominal surgical procedure.
It is therefore desirable to provide a surgical tool and method for using the same which will not only reduce vertebral displacement, but which tool and method of use will likewise improve the overall method of treatment of conditions involving misalignment of the vertebrae and which will permit surgical treatment via an anterior or intra-abdominal surgical approach.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.